1. Technical Field of the Invention
The invention relates to an apparatus and method for printing image information having a specific orientation on sheets of a receiving material. More particularly, this invention relates to a method and apparatus for printing two images on a receiving material with a printer which rotates at least one of the images with a rotation method that utilizes minimal memory space to rotate images. The invention also relates to a method and apparatus for rotating a series of images to position pairs of images from the image series in a specific orientation on a corresponding series of receiving materials.
2. Description of Related Art
In general, printing two images having an identical orientation on a single sheet is known. For example, U.S. Pat. No. 4,763,167 describes a copying method in which the image information from two different original sheets is read or scanned successively and, after storage and processing, is printed on one copy sheet such that the reading orientations of the two images are identical and are perpendicular to the long side of the copy sheet. With this conventional method, it is possible to obtain copy sheets which may be folded in the middle, between the images, in order to form a folded sheet as shown in the ""167 patent. A plurality of such copy sheets may be assembled to create a manual or booklet.
According to another known method of reproduction, original images are printed twice on one copy sheet and then the copy sheet is cut through between the two (identical) images, thus giving one page for each of two booklets, e.g. manuals, to be produced.
Alternatively, instead of a booklet with a fold line, spine, or some other binding portion i.e. a part of the sheet suitable for binding a plurality of such sheets into a collection, at the center of the sheet, it is possible to utilize a binding portion provided at the left-hand or right-hand (short side) of the copy sheets. To print on sheets provided with such alternative binding portions, two images are typically read out of an image or page memory with a 0xc2x0 or 180xc2x0 rotation and then printed on the sheet accordingly.
Increasingly, when images from original sheets are reproduced, copy sheets which may or may not be completely adapted to the method of subsequent collation, e.g. collation by way of ring binding, thread sewing, screw binding, stapling, clipping, gluing, thermo-binding etc., are being used for example, copy sheets provided with a binding portion on two short sides such as  including suitable for storage in a ring binder are often used to reproduce images. Such copy sheets, which may or may not be connected in continuous form, are typically cut in half at a perforation leaving two half-sheets each of which includes a binding portion on a short side thereof. If the above-described conventional methods of reproduction are used with such copy sheets, identical pages would be obtained after cutting through the sheet, but the perforated edges would be at opposite sides, something which is quite unacceptable.
Furthermore, if two different pages, e.g. two consecutive pages, are imaged on copy sheets provided with a binding portion on two short sides, it would be a complex matter to collate the booklets, because when the copy sheet is cut through the center the pages would have to be arranged alternately.
Also, in conventional duplex printing, the image of the first original is printed on one side of the copy sheet and then the copy sheet is flipped 180xc2x0 about the short axis and then the image of the second information sheet is printed on the second side of the copy sheet. In this case, action must be taken to keep the image orientation the same on both sides of the copy sheet.
An example of conventional duplex printing is described in Applicants"" commonly assigned European Patent Application 0 628 922. According to the method known therefrom, optimal use is made of the memory space by storing the image data of the first original image in ascending address sequence in the memory starting from the first free memory address, but storing the image data of the second original image in reverse address sequence in the memory starting from the last free memory address. On read-out, the image data are always read out of the memory in ascending address sequence, so that the image data of the second original image are fed to the printer with an automatic 180xc2x0 rotation.
Furthermore, conventional image rotation typically writes the data of an image line-by-line into a bit map memory and then reads out the data column-by-column (from bottom to top) from the memory. After the read-out is completed and the memory is empty, the data of the next image to be rotated can then be written into the memory. In other words, before the data of each subsequent image can be written into the memory it is necessary to wait until the read-out of the preceding image is completed.
To remedy the delay caused by this conventional rotation method, it is known to utilize two memories which are used alternately: while one image is being read out of the first memory, the next image is being written into the second memory. However, this conventional remedy increases the cost and complexity of the resultant system.
Furthermore, it should be noted that a method of writing image data from an image within a series of images into a memory at memory locations that have been freed by reading out the preceding image in the series is described in U.S. Pat. No. 5,151,976. The ""976 patent writes an image into a memory line-by-line and then reads-out this image in a fixed, sawtooth pattern to rotate the image through 90xc2x0 plus a reflection. Because of the limitations on the rotation angle, the fixed, sawtooth addressing formula described in the ""976 patent is therefore not suitable rotating images as intended by the present invention, nor is it suitable for changing the angle of rotation for each image optionally in a series of images.
A main object of the invention is to provide improvements in which address the above problems. To this end, the present invention includes a method and apparatus which prints two images on a receiving material such that the two images are situated next to one another with reading orientations of the images rotated through 180xc2x0 relative to one another and forming a right angle with the sides of the receiving material which are provided with a binding portion.
By utilizing this aspect of the invention, the image orientation with respect to the associated short side of the copy sheet will be the same for both images. If two different originals are copied on one copy sheet, two identically oriented consecutive pages will be obtained which may be easily collated into into a single booklet. Due to efficiency considerations, however, it is sometimes preferably to image a single original image twice on the copy sheet, and according to the invention this will result in two identically oriented pages which may be easily collated into two , consecutively made  booklets.
The method and apparatus according to the invention can be applied to any printer, irrespective of the formats of the original sheet, on the one hand, and the copy sheet, on the other hand. Thus it is possible to use one A4 original sheet read into the copying machine in the plait position, and an A4 copy sheet which is delivered by the printer in the portrait position, in which case the original image rotation should take place through +90xc2x0 and xe2x88x9290xc2x0 respectively, with a reduction of 71%. A landscape sheet can also be used, the image of which may be reproduced twice on a copy sheet that is delivered in the portrait position, in which case rotation will be through 180xc2x0 for one of the images.
For the method and apparatus of the invention, there is no need to start with original sheets scanned by a scanner and with the resulting data then processed. It is possible to generate the image data page-wise with a computer using a suitable program and then rotate and print the generated image data using the inventive methods. In this application, the term xe2x80x9coriginal sheetxe2x80x9d also refers to an image generated by a computer.
According to another aspect of the present invention, an attractive manner of rotating the image data is applied, using just one memory having a capacity which is only slightly larger than that required to contain the image data. According to this aspect, the invention offers a rotation procedure for blocks of image information each corresponding to an original image from a series of at least two original images, using a memory with locations corresponding to a matrix of image elements, or blocks of image elements, of an original image, hereinafter referred to as xe2x80x9cimage data.xe2x80x9d
The inventive rotation procedure includes writing image data into the memory according to a first sequence of memory locations and reading out of the memory the written-in image data according to a second sequence of memory locations, wherein the writing into the memory of image data from the series is affected in substantially the same sequence as that in which image data of a preceding image in the series was read out. Furthermore, at the start of a series of images, the image data are written into consecutive memory locations.
Still further, the inventive method is such that for a change of orientation in the form of a rotation through an angle of {0xc2x0,+90xc2x0, +180xc2x0, xe2x88x9290xc2x0} image data are read out of memory locations of the memory in a sequence given by an address sequence series which is built up from series elements each designating a memory location of the memory in which an image element or a block of image elements of the first matrix is stored. The series elements may be calculated by the following equation:                               series          ⁢                      xe2x80x83                    ⁢                      element            ⁡                          (                              i                j                            )                                      =                                            (                              i                *                                  ∏                                      xe2x80x83                                    ⁢                                      x                    k                                                              )                        ⁢                                                            modulo                  j                                                  k                  =                  1                                            ⁡                              (                                                                            d                      1                                        *                                          d                      2                                                        +                  1                                )                                              -          1                                    (        1        )            
where i=position within the address sequence series, where
1xe2x89xa6ixe2x89xa6d1*d2,
j=serial number of the relevant image in the series,
d1=number of columns of the matrix,
d2=number of rows of the matrix, Xk=parameter related to the required angle of rotation for the kth image in the series of images,
where Xk=1 for a rotation through 0xc2x0,
xe2x88x92d1 for a rotation through +90xc2x0.
xe2x88x921 for a rotation through +180xc2x0, and
d1 for a rotation through xe2x88x9290xc2x0.
The image data of an image from the series are simultaneously written into the memory while the image data of the preceding image of the series are being read out, either by writing new data directly onto a location that has just become free (or by writing onto a location according to a lag-time of a variable number of memory locations) Significantly, the writing operations are performed according to the same sequence of memory locations that were used to read out the preceding image in the series.
By overwriting the memory in this way, it is no longer possible to obtain a fixed relationship between the positions of the image data in the image matrix and the positions of the memory locations in the memory. This problem can be solved with good memory address management, but management in the form of a table with addresses takes up valuable memory space so that some of the gains in memory size reduction are lost. Instead of such complex memory management utilizing a table, the above addressing formula (1) is applied by the invention. This inventive procedure requires only minimal memory space and processor capacity.
Addressing formula (1) is not only suitable for rotating individual pixels but also for rotating blocks of pixels. In fact, very fast conventional hardware circuits which can rotate square blocks of pixels (e.g. 8xc3x978) through angles of 90xc2x0 and multiples thereof may be used in conjunction with the invention. When these conventional circuits are used with the invention, the image matrix is divided into blocks of pixels and the blocks are written into and read out of the memory as a unit with inventive addressing formula (1) indicating the positions of the blocks in the memory.
By employing the inventive addressing formula, it is always possible to find the correct address sequence series for writing an image into the memory following a read-out of a preceding image. By simply adjusting of the value of xk, the invention also permits each image in the series to be rotated through a different rotation angle because addressing formula (1) determines the correct addresses for each of the desired rotations.
The rotation method according to the invention can also be applied to making duplex copies. In the inventive method and apparatus for making duplex copies, the original images are read consecutively into the memory and the read-out of images from the memory takes place consecutively after each write-in accordance with an address sequence given by the address sequence series whose elements are defined by formula (1), wherein the selected angles of rotation differ by 180xc2x0 relative to one another and wherein the data of the two read-out operations are fed successively to the printer for consecutive imaging on one side and then the other side of a copy sheet, respectively.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.